json.cpp

/**
 * \file json.cpp
 */
 
#include "json.h"
#include <QLocale>

static QString sanitizeString(QString str)
{
	str.replace(QLatin1String("\\"), QLatin1String("\\\\"));
	str.replace(QLatin1String("\""), QLatin1String("\\\""));
	str.replace(QLatin1String("\b"), QLatin1String("\\b"));
	str.replace(QLatin1String("\f"), QLatin1String("\\f"));
	str.replace(QLatin1String("\n"), QLatin1String("\\n"));
	str.replace(QLatin1String("\r"), QLatin1String("\\r"));
	str.replace(QLatin1String("\t"), QLatin1String("\\t"));
	return QString(QLatin1String("\"%1\"")).arg(str);
}

static QByteArray join(const QList<QByteArray> &list, const QByteArray &sep)
{
	QByteArray res;
	foreach(const QByteArray &i, list)
	{
		if(!res.isEmpty())
		{
			res += sep;
		}
		res += i;
	}
	return res;
}

/**
 * parse
 */
QVariant Json::parse(const QString &json)
{
	bool success = true;
	return Json::parse(json, success);
}

/**
 * parse
 */
QVariant Json::parse(const QString &json, bool &success)
{
	success = true;

	//Return an empty QVariant if the JSON data is either null or empty
	if(!json.isNull() || !json.isEmpty())
	{
		QString data = json;
		//We'll start from index 0
		int index = 0;

		//Parse the first value
		QVariant value = Json::parseValue(data, index, success);

		//Return the parsed value
		return value;
	}
	else
	{
		//Return the empty QVariant
		return QVariant();
	}
}

/**
 * serialize
 */
QByteArray Json::serialize(const QVariant &data)
{
	bool success = true;
	return Json::serialize(data, success);
}

/**
 * serialize
 */
QByteArray Json::serialize(const QVariant &data, bool &success)
{
	QByteArray str;
	success = true;

	if(!data.isValid()) // invalid or null?
	{
		str = "null";
	}
	else if((data.type() == QVariant::List) || (data.type() == QVariant::StringList)) // variant is a list?
	{
		QList<QByteArray> values;
		const QVariantList list = data.toList();
		foreach(const QVariant& v, list)
		{
			QByteArray serializedValue = serialize(v);
			if(serializedValue.isNull())
			{
				success = false;
				break;
			}
			values << serializedValue;
		}

		str = "[" + join( values, "," ) + "]";
	}
	else if(data.type() == QVariant::Map) // variant is a map?
	{
		const QVariantMap vmap = data.toMap();
		QMapIterator<QString, QVariant> it( vmap );
		str = "{";
		QList<QByteArray> pairs;
		while(it.hasNext())
		{
			it.next();
			QByteArray serializedValue = serialize(it.value());
			if(serializedValue.isNull())
			{
				success = false;
				break;
			}
			pairs << sanitizeString(it.key()).toUtf8() + ":" + serializedValue;
		}
		str += join(pairs, ",");
		str += "}";
	}
	else if (data.isNull())
	{
		str = "null";
	}
	else if((data.type() == QVariant::String) || (data.type() == QVariant::ByteArray)) // a string or a byte array?
	{
		str = sanitizeString(data.toString())
#if QT_VERSION >= 0x050000
		.toUtf8();
#else
		.toAscii();
#endif
	}
    else if(data.type() == QVariant::Double) // double?
    {
#if (QT_VERSION >= QT_VERSION_CHECK(5,7, 0))
        str = QByteArray::number(data.toDouble(), 'f', QLocale::FloatingPointShortest);
#else
        str = QByteArray::number(data.toDouble());
#endif
    }
	else if (data.type() == QVariant::Bool) // boolean value?
	{
		str = data.toBool() ? "true" : "false";
	}
	else if (data.type() == QVariant::ULongLong) // large unsigned number?
	{
		str = QByteArray::number(data.value<qulonglong>());
	}
	else if ( data.canConvert<qlonglong>() ) // any signed number?
	{
		str = QByteArray::number(data.value<qlonglong>());
	}
	else if (data.canConvert<QString>()) // can value be converted to string?
	{
		// this will catch QDate, QDateTime, QUrl, ...
		str = sanitizeString(data.toString())
#if QT_VERSION >= 0x050000
		.toUtf8();
#else
		.toAscii();
#endif
	}
	else
	{
		success = false;
	}
	if (success)
	{
		return str;
	}
	else
	{
		return QByteArray();
	}
}

/**
 * parseValue
 */
QVariant Json::parseValue(const QString &json, int &index, bool &success)
{
	//Determine what kind of data we should parse by
	//checking out the upcoming token
	switch(Json::lookAhead(json, index))
	{
		case JsonTokenString:
			return Json::parseString(json, index, success);
		case JsonTokenNumber:
			return Json::parseNumber(json, index);
		case JsonTokenCurlyOpen:
			return Json::parseObject(json, index, success);
		case JsonTokenSquaredOpen:
			return Json::parseArray(json, index, success);
		case JsonTokenTrue:
			Json::nextToken(json, index);
			return QVariant(true);
		case JsonTokenFalse:
			Json::nextToken(json, index);
			return QVariant(false);
		case JsonTokenNull:
			Json::nextToken(json, index);
			return QVariant();
		case JsonTokenNone:
			break;
	}

	//If there were no tokens, flag the failure and return an empty QVariant
	success = false;
	return QVariant();
}

/**
 * parseObject
 */
QVariant Json::parseObject(const QString &json, int &index, bool &success)
{
	QVariantMap map;
	int token;

	//Get rid of the whitespace and increment index
	Json::nextToken(json, index);

	//Loop through all of the key/value pairs of the object
	bool done = false;
	while(!done)
	{
		//Get the upcoming token
		token = Json::lookAhead(json, index);

		if(token == JsonTokenNone)
		{
			 success = false;
			 return QVariantMap();
		}
		else if(token == JsonTokenComma)
		{
			Json::nextToken(json, index);
		}
		else if(token == JsonTokenCurlyClose)
		{
			Json::nextToken(json, index);
			return map;
		}
		else
		{
			//Parse the key/value pair's name
			QString name = Json::parseString(json, index, success).toString();

			if(!success)
			{
				return QVariantMap();
			}

			//Get the next token
			token = Json::nextToken(json, index);

			//If the next token is not a colon, flag the failure
			//return an empty QVariant
			if(token != JsonTokenColon)
			{
				success = false;
				return QVariant(QVariantMap());
			}

			//Parse the key/value pair's value
			QVariant value = Json::parseValue(json, index, success);

			if(!success)
			{
				return QVariantMap();
			}

			//Assign the value to the key in the map
			map[name] = value;
		}
	}

	//Return the map successfully
	return QVariant(map);
}

/**
 * parseArray
 */
QVariant Json::parseArray(const QString &json, int &index, bool &success)
{
	QVariantList list;

	Json::nextToken(json, index);

	bool done = false;
	while(!done)
	{
		int token = Json::lookAhead(json, index);

		if(token == JsonTokenNone)
		{
			success = false;
			return QVariantList();
		}
		else if(token == JsonTokenComma)
		{
			Json::nextToken(json, index);
		}
		else if(token == JsonTokenSquaredClose)
		{
			Json::nextToken(json, index);
			break;
		}
		else
		{
			QVariant value = Json::parseValue(json, index, success);

			if(!success)
			{
				return QVariantList();
			}

			list.push_back(value);
		}
	}

	return QVariant(list);
}

/**
 * parseString
 */
QVariant Json::parseString(const QString &json, int &index, bool &success)
{
	QString s;
	QChar c;

	Json::eatWhitespace(json, index);

	c = json[index++];

	bool complete = false;
	while(!complete)
	{
		if(index == json.size())
		{
			break;
		}

		c = json[index++];

		if(c == '\"')
		{
			complete = true;
			break;
		}
		else if(c == '\\')
		{
			if(index == json.size())
			{
				break;
			}

			c = json[index++];

			if(c == '\"')
			{
				s.append('\"');
			}
			else if(c == '\\')
			{
				s.append('\\');
			}
			else if(c == '/')
			{
				s.append('/');
			}
			else if(c == 'b')
			{
				s.append('\b');
			}
			else if(c == 'f')
			{
				s.append('\f');
			}
			else if(c == 'n')
			{
				s.append('\n');
			}
			else if(c == 'r')
			{
				s.append('\r');
			}
			else if(c == 't')
			{
				s.append('\t');
			}
			else if(c == 'u')
			{
				int remainingLength = json.size() - index;

				if(remainingLength >= 4)
				{
					QString unicodeStr = json.mid(index, 4);

					int symbol = unicodeStr.toInt(0, 16);
					
					s.append(QChar(symbol));

					index += 4;
				}
				else
				{
					break;
				}
			}
		}
		else
		{
			s.append(c);
		}
	}

	if(!complete)
	{
		success = false;
		return QVariant();
	}

	return QVariant(s);
}

/**
 * parseNumber
 */
QVariant Json::parseNumber(const QString &json, int &index)
{
	Json::eatWhitespace(json, index);

	int lastIndex = Json::lastIndexOfNumber(json, index);
	int charLength = (lastIndex - index) + 1;
	QString numberStr;

	numberStr = json.mid(index, charLength);
	
	index = lastIndex + 1;

	return QVariant(numberStr.toDouble(NULL));
}

/**
 * lastIndexOfNumber
 */
int Json::lastIndexOfNumber(const QString &json, int index)
{
	int lastIndex;

	for(lastIndex = index; lastIndex < json.size(); lastIndex++)
	{
		if(QString("0123456789+-.eE").indexOf(json[lastIndex]) == -1)
		{
			break;
		}
	}

	return lastIndex -1;
}

/**
 * eatWhitespace
 */
void Json::eatWhitespace(const QString &json, int &index)
{
	for(; index < json.size(); index++)
	{
		if(QString(" \t\n\r").indexOf(json[index]) == -1)
		{
			break;
		}
	}
}

/**
 * lookAhead
 */
int Json::lookAhead(const QString &json, int index)
{
	int saveIndex = index;
	return Json::nextToken(json, saveIndex);
}

/**
 * nextToken
 */
int Json::nextToken(const QString &json, int &index)
{
	Json::eatWhitespace(json, index);

	if(index == json.size())
	{
		return JsonTokenNone;
	}

	QChar c = json[index];
	index++;
#if QT_VERSION >= 0x050000
    switch(c.toLatin1())
#else
    switch(c.toAscii())
#endif
	{
		case '{': return JsonTokenCurlyOpen;
		case '}': return JsonTokenCurlyClose;
		case '[': return JsonTokenSquaredOpen;
		case ']': return JsonTokenSquaredClose;
		case ',': return JsonTokenComma;
		case '"': return JsonTokenString;
		case '0': case '1': case '2': case '3': case '4':
		case '5': case '6': case '7': case '8': case '9':
		case '-': return JsonTokenNumber;
		case ':': return JsonTokenColon;
	}

	index--;

	int remainingLength = json.size() - index;

	//True
	if(remainingLength >= 4)
	{
		if (json[index] == 't' && json[index + 1] == 'r' &&
			json[index + 2] == 'u' && json[index + 3] == 'e')
		{
			index += 4;
			return JsonTokenTrue;
		}
	}

	//False
	if (remainingLength >= 5)
	{
		if (json[index] == 'f' && json[index + 1] == 'a' &&
			json[index + 2] == 'l' && json[index + 3] == 's' &&
			json[index + 4] == 'e')
		{
			index += 5;
			return JsonTokenFalse;
		}
	}

	//Null
	if (remainingLength >= 4)
	{
		if (json[index] == 'n' && json[index + 1] == 'u' &&
			json[index + 2] == 'l' && json[index + 3] == 'l')
		{
			index += 4;
			return JsonTokenNull;
		}
	}

	return JsonTokenNone;
}